The invention relates to a device for detecting discontinuities in the communication of a sensor with a patient.
Modern medical practice uses a variety of sensors juxtaposed with a patient for sensing a condition of the patient. For example, heart beat sensors, brain wave sensors and skin temperature sensors are now widely used. Each of these sensors is brought into close proximity with the patient so as to penetrate slightly into the patient, be in surface, skin contact with the patient, or be slightly spaced from the patient by a tape or gel, all of which are described here as juxtaposing the sensor with the patient.
If the sensors separate from the patient to a nonjuxtaposed position, they will lose sensing communication with the patient. The sensors therefore are usually adhesively taped or strapped to the patient to try to hold them in their operative, juxtaposed position. The arrangement for holding the sensor on the patient cannot be overly secure, however, in order to provide ready disconnect to allow emergency services to be provided to the patient, to allow the patient to be transferred, to provide for patient comfort in avoiding excessive pressures and allowing body movement and, of course, to allow final removal of the sensor.
A still further problem particularly limits the adhesive taping of sensors to infants. The infants skin is very fragile. The adhesive on the tape thus tends to tear the infant's skin when it is made sufficiently adherant to resist detachment from the infant's movement and then is removed for servicing the infant. The adhesive for taping sensors to infants thus cannot be as strong as would be desired merely for holding the sensor on the infant. As a result of all these limitations on holding a sensor on both adults and infants, the sensor can be dislodged by patient movement or other inadvertent action.
Sometimes the resulting loss of sensor communication with the patient is indicated by the corresponding loss of sensor function. For example, with a heart beat sensor, separation of the sensor from the patient stops the sensing of heart beats. An alarm on the heart beat monitor connected to the sensor will then be triggered, but the alarm will not indicate whether the absence of a sensed heart beat has occurred because the patient's heart has stopped, or because the sensor has lost communication with the patient. When the patient is unconscious, valuable time can then be lost in checking for the patient's heart beat to determine the cause of the alarm.
In other applications there may be even less indication of the loss of sensor communication with the patient. For example, the care of burn victims and infants often includes a radiant heater for maintaining the patient's body temperature. The heater is controlled with a skin temperature sensor to supply heat to the patient as indicated by the patient's skin temperature. If the sensor becomes dislodged from the patient's skin, overheating or underheating the patient can result from the consequent discontinuity in the communication between the sensor and patient. The over- or underheating, moreover, cannot be detected from the operation of the heater as previously proposed, except at extremes of over- or underheating the patient because of the wide range of heating conditions which are required for variations in patient and ambient temperature.
Thus, for example, the normal body movement of an infant in an incubator or other early-care arrangement including a radiant heater for heating the infant can dislodge a temperature sensor which has been taped to the infant's skin only strongly enough to avoid damage to infant's skin when the sensor is intentionally removed. The dislodged sensor will then sense an ambient temperature to which the heater responds. The heater then can seriously over- or underheat the infant. Instructions to the infant not to remove the sensor are clearly as ineffective in avoiding the problem as response from the infant to the over- or underheating is in detecting it.